The invention relates to an amplifier arrangement comprising a differential amplifier having two input terminals for receiving an input voltage and a differential-to-single-ended converter having an output terminal for supplying an output current, said converter including a first and a second transistor of a first conductivity type whose source electrodes are coupled to a first supply terminal and whose gate electrodes are coupled together, and a third and a fourth transistor of the first conductivity type arranged in cascade with the first and the second transistor, respectively, and having their gate electrodes coupled together.
An amplifier arrangement of this type can be generally used as an operational amplifier having a relatively high gain and a relatively large bandwidth. Such an arrangement can be particularly used in video circuits, switched capacitor circuits and sample and hold circuits.
Such an amplifier arrangement is known from the book "Analysis and Design of Analog Integrated Circuits" P. R. Gray; R. G. Meyer, 1984 John Wiley and Sons Inc., page 753, FIG. 12.38.
In this known arrangement, the differential-to-single-ended converter is constituted by an improved Wilson current mirror in which the gate electrodes of both the first transistor and the third transistor are connected to the drain electrode.
This arrangement has the drawback that the output voltage swing of the amplifier arrangement is comparatively small. In fact, the drain electrode of the fourth transistor connected to the output can only be driven up to the sum of one threshold voltage and two saturation voltages with respect to the negative supply terminal.